[committed] analyzer: round-trip pointer-equality through intptr_t

Message ID 20200206194557.11472-1-dmalcolm@redhat.com
State New
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  • [committed] analyzer: round-trip pointer-equality through intptr_t
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Commit Message

David Malcolm Feb. 6, 2020, 7:45 p.m.
When investigating how the analyzer handles malloc/free of Cray pointers
in gfortran I noticed that that analyzer was losing information on
pointers that were cast to an integer type, and then back to a pointer
type again.

The root cause is that region_model::maybe_cast_1 was only preserving
the region_svalue-ness of the result if both types were pointers,
instead returning an unknown_svalue for a pointer-to-int cast.

This patch updates the above code so that it attempts to use a
region_svalue if *either* type is a pointer

Doing so allows the analyzer to recognize that the same underlying
region is in use through various casts through integer types.

Successfully bootstrapped & regrtested on x86_64-pc-linux-gnu.
Pushed to master as cb273d81a45092ceee793f0357526e291f03c7b7.

gcc/analyzer/ChangeLog:
	* region-model.cc (region_model::maybe_cast_1): Attempt to provide
	a region_svalue if either type is a pointer, rather than if both
	types are pointers.

gcc/testsuite/ChangeLog:
	* gcc.dg/analyzer/torture/intptr_t.c: New test.
---
 gcc/analyzer/region-model.cc                  |  2 +-
 .../gcc.dg/analyzer/torture/intptr_t.c        | 28 +++++++++++++++++++
 2 files changed, 29 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/gcc.dg/analyzer/torture/intptr_t.c

-- 
2.21.0

Patch

diff --git a/gcc/analyzer/region-model.cc b/gcc/analyzer/region-model.cc
index 571ae6e4d56..8b57a623084 100644
--- a/gcc/analyzer/region-model.cc
+++ b/gcc/analyzer/region-model.cc
@@ -5004,7 +5004,7 @@  region_model::maybe_cast_1 (tree dst_type, svalue_id sid)
     return sid;
 
   if (POINTER_TYPE_P (dst_type)
-      && POINTER_TYPE_P (src_type))
+      || POINTER_TYPE_P (src_type))
     {
       /* Pointer to region.  */
       if (region_svalue *ptr_sval = sval->dyn_cast_region_svalue ())
diff --git a/gcc/testsuite/gcc.dg/analyzer/torture/intptr_t.c b/gcc/testsuite/gcc.dg/analyzer/torture/intptr_t.c
new file mode 100644
index 00000000000..847ba626350
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/analyzer/torture/intptr_t.c
@@ -0,0 +1,28 @@ 
+/* { dg-skip-if "" { *-*-* } { "-fno-fat-lto-objects" } { "" } } */
+
+#include <stdlib.h>
+
+typedef __INTPTR_TYPE__ intptr_t;
+typedef __UINTPTR_TYPE__ uintptr_t;
+
+void test_1 (void)
+{
+  intptr_t ip;
+  void *p = malloc (1024);
+  ip = (intptr_t)p;
+  free ((void *)ip);
+} /* { dg-bogus "leak" } */
+
+void test_2 (void)
+{
+  uintptr_t uip;
+  void *p = malloc (1024);
+  uip = (uintptr_t)p;
+  free ((void *)uip);
+} /* { dg-bogus "leak" } */
+
+void test_3 (intptr_t ip)
+{
+  free ((void *)ip); /* { dg-message "first 'free'" } */
+  free ((void *)ip); /* { dg-warning "double-'free'" } */
+}